(564b) How Do Hemicellulosesaffect the Lignocellulose Enzymatic Digestibility

 Hemicelluloses have been considered as a major factor limiting the enzymatic digestibility of lignocellulosic cellulose for glucose releasing. To study how hemicelluloses affect the enzymatic hydrolysis of lignocellulose, dilute acid was applied for removing hemicelluloses of wheat straw under mild conditions to obtain samples with different hemicelluloses content. To investigate the interaction of lignin with hemicelluloses, sodium chlorite was used to selectively remove lignin. It was found that with a high lignin content (28~38%), cellulose conversion increased with decrease of hemicelluloses (noted as xylan) content, but the highest cellulose conversion (~2% xylan content) was just about 65%. However, when lignin content was low (~4%), hemicelluloses showed nosignificant negative effect on cellulose hydrolysis, and the final cellulose conversion could be as high as 90% even if the xylan content was as high as 28.25%. It seemed that lignin is more negative for the enzymatic hydrolysis of lignocellulose. Xylan was added to hydrolysis of pure cellulose to study how hemicellulose affect the lignocellulose enzymatic digestibility. The results indicated that xylan, especially soluble xylan had anegative effecton cellulose hydrolysis. And the existence of xylan decreased cellulase adsorption on cellulose. Further study is needed to investigate the mechanism.